High-quality surfaces are used as an aid in “high end quality” positioning of car equipment, household appliances, entertainment electronics, sports equipment and industrial surfaces which are easy to clean.
Cleanable surfaces must have in addition suitable scratch resistance and high chemical resistance in order that they retain the appearance of new devices for as long as possible.
These devices are intended at the same time to have high reliability with respect to being dropped, impact and shock and therefore have tough, protective casings. Hence a material which displays a difficult property combination of high-gloss surface, toughness and scratch resistance is required for the moulded article.
Numerous patents describe the impact strength modification of polyamides with different elastomeric modifiers. The impact strength in partially crystalline polyamides can hence be improved.
The impact strength modification of amorphous products is rarely required since the modifiers greatly influence the surfaces. Roughness, gloss and homogeneity are greatly impaired so that moulded articles which are visually apparent in an application are no longer accepted or require to be varnished.
Amorphous polyamides without impact modifiers have a good surface but do not achieve notch impact strength values of above 15 kJ/m2. The same applies for blends of amorphous and partially crystalline polyamides in which the surface quality is likewise good but the impact strength does not suffice.
EP 1 847 569 A1 describes for example transparent polyamides which are blended with polyester amides and have increased notch impact strength. No gloss values are indicated and in particular the comparative examples with the impact modifiers reveal severe clouding (haze).
EP 1 227 131 B1 describes a transparent polyamide composition. In the moulding compound according to this publication, a partially crystalline polyamide forms the basis for a blend, the notch impact strength of which can be improved by means of impact modifiers. The effect on the gloss is however inadequate.
Also moulding compounds containing polyphenylene ethers, described for example in EP 0 654 505 B1, having polyamides which can if necessary be modified with respect to impact strength are known for having inadequate properties with respect to the gloss values.
Further polyamide moulding compounds are described in DE 10 2005 023 420 A1, DE 198 21 719 A1 and EP 1 882 719 A1.